One apparently called for the health secretary to be replaced, another said the Bill should be dropped, and the third likened the NHS reforms to the poll tax.

Labour leader Ed Miliband has written to all members of the House of Lords urging them to block key measures in the Bill.

"On behalf of my Party, I want to extend this offer to peers of all parties and of none: we will work with you to stop this Bill damaging the NHS," he wrote.

"Recent weeks and months have shown just how widely the concerns about this Bill are shared - not just among patients and the public, but also among doctors, nurses and other NHS staff.

"The government would have us believe that those who oppose this Bill are 'vested interests'. I think that is deeply insulting to people who have devoted their lives to working in the NHS and care about its future.

"I want you to know that Labour has made an offer to put party differences aside and work with the government on reform objectives we all share, such as greater clinical involvement in commissioning and the funding of social care.

"But ultimately, the NHS is too important to stand back and let this Bill damage it. I hope we can all work together to protect the future of our National Health Service."